Micrometer-calipers.



H. s. HUBBELL.

MICROMETER CALIPERS.

APPLICATION FILED SEPT. 2.1916.

1,267,075 Paten-ted May 21, 1918.

NETE@ STATES ATENT QE@ 0F NEW YORK.

HENRY S. HUBBELL, OF ASEBURNHAM, MASSACHUSETTS, ASSIGNOR T0 T. R. ALMOND MANUFACTURING COMPANY, OF .ASHBURNHAM, MASSACHUSETTS, A CORPOIIIAZIlil'l MICROMETER-CALIPERS.

Lemma.

Specification of Letters Patent.

Patented May 2t, NMS.

Epplication filed September 2, 1916-. Serial No. 118,247.

To all rwhom t may concern.'

Be it known that I, HENRY S. HUBBELL, a citizen of the United States, residing at Ashburnham, Worcester county, State of Massachusetts, have invented certain new and' Auseful Improvements in Micrometer- Calipers, of which the following is a specilication. y

My invention relates to micrometer calipers such as are commonly employed in the arts by expert metal workers, tool makers and mechanics generally vfor the accurate measurement of thicknesses, diameters and other dimensions.

Mierometer calipers such as are above referred to generally comprise a U-shaped frame having an anvil at the end of one limb and a spindle rotatably engaged with the end of the other limb through a very fine and accurately cut screw thread with which part of the spindle is provided.

Two difficulties are usually encountered in calipers of this kind, one being that of securing and maintaining an exact fit1 free from play, wabble or lost motion, between the screw of the spindle and the corresponding thread or nut of the frame; and the other being that of insuring that the spindle shallalways stop vat exactly the same point,

for the same measured dimension interposed between anvil and spindle end, in the hands of the average mechanic.

lt is the object of my invention to provide a construction for micrometer calipers of the type specified which shall eliminate both of these difficulties.

My invention will be better understood by referring to the accompanying drawings in which Figure l represents a side elevation of a micrometer caliper embodying myy invention; Fig. 2 is a detail represent-ing an enlarged axial section, part elevation, through the spindle, frame, sleeve ,and dial barrel; Fig. 3 represents a detail elevation, enlarged to the same scale as Fig. 2, showing a part of the frame witha modified form of barrel according to my invention; Fig. vIl: represents a section taken along the line 4 4 of Fig. 3; Fig `5 is a view` `similar to Fig. 3, showing another modified form, of barrell according to my invention; and Fig. 6 is an end view from the right of Fig. 5.

In the drawings, 1 indicates the U-shaped frame of the micrometer caliper; 2 the anvil; 3 the spindle having an accurate sliding fit. with the bearing 4f, part of the spindlebeing provided with an accurately cut screw thread 5 having screw thread engagement with the interior end portion of the barrel 6; and 7 the scale barrel which is removably but tightly fitted to the exterior of that part of barrel 6 which lies between the frame and the interior screw threads of said barrel.

The spindle 3, at its outer end, is provided with the usual scale sleeve 8 which is adapted to slip closely but freely over scale barrel 7. The free end of scale sleeve 8 is beveled to a thin edge and this bevel provided with the usual graduation lines to indicate fractional revolutions of the spindle.

Scale barrel 7 is provided with the usual lineally disposed graduations adapted to cooperate with the bevel edge of scale sleeve 8 to indicate complete revolutions of the spindle.

The interior threads of barrel 6, which are in engagement with screw thread 5 of spindle 3, extend from the outer end of the barrel for about one-third of the distance toward the frame l. The remaining interior portion of the barrel, up to the bearing 4L is reamed out, or otherwise formed to a larger diameter,l so that its interior wall is spaced from the spindle.

The barrel 6 is preferably of uniform wall thickness over that portion of its length which is spaced away from the spindle and then tapered inwardly and centrally over the remaining portion of its length which has the interior'screw thread.

The tapered portion of barrel 6 is screw threaded from the base of the taper t0 the end of the barrel and provided with a nut 9. This tapered portion is also provided with longitudinal slots which extend from end to base. As shown, there are three of these slots, spaced annularly 120 apart although four or any other number may be used? At' the base of each slot a hole l0, of

terior screw thread 5 of the barrel." In this.

wayv any tendency to play or lost motion causedby wear is automatically taken-up .inasmuch as the ngers will follow up the screw threadof the spindle at all times irrespective of theamount of Wear. vThis tendency of the fingers to spring inwardlyarnd to follow. up the spindle is assisted 'reatly by reason of. the holes 10 since the wi th ofthe fingers, at their base between holes 10,' is comparatively small and the wall portion of the fingers between the holesl approximates,y a flat-surface so as to enable the fingers to spring linwardly and withoutJ anyv tendency to buckle. n

l An important feature of my invention is the use of what is vcommonly known as a ratchetfscrew thread upon the spindleand forthe interior c'operating threads ofthe taperedportions ofthe barrel. By aratchet screw thread is meant a thread one side of which is substantially perpendicular to the axis4 of' the screw while .the other side is inclined as inan ordinary V screw. By having the perpendicular side of the spindle thread face away from the frame and the corresponding face `of the interiorV thread of the tapered portion of barrel 6 face toward the frame, it is obvious that when the spindle is screwed down upon any piece to be measured, which piece is itself abutted against the anvil 2, the spindle will tend to be positively and definitely stopped as soon as it abuts against the piece to be measured inasmuch as the 'two fiat sides .of the coperating screw threads of spindle and barrel will be pressed together along line of resultant pressure coincident with the aXis of the spindle. When the spindle screw thread and the coperating interior screw thread of the end of barrel` 6 are V-shaped, then, as soon` as the spindle is abutted against the piecev tobe measured, any further rotatory force imparted to the spindle willberesolved y partlyy into a force acting radially outward to push the fingersll away from the screw threads of thevspindle, thusgiving a false reading of the micrometer. As micrometers are ordinarily made with a Ve-threaded spindle, errors in their usefare almost ,certain-,to creep in eXceptin the hands of the most eX- pert mechanicsinasmuch as it almost impossible to applyjust the same amount lof force in settinglthe spindle up againstthe object to be measured. on successive measurements. Diierent mechanics also measure the same dimension differently because of the fact that one mechanic is accustomed to use one degree of force in setting up the spindle against the object to' be measured', while another mechanic is likely'to use another degree of force. With the spindle provided with a ratchet thread", as in my invention, the same readingwill-r be obtainedior each measurement made on the same'olojgeet within very small limits of error even when made by mechanics of' widely differing de ees of skill, unless, of course, a degree: of force be applied which is unthinkable in the case of any' trained artisan.

If a very greatly excessive force be applied to rotatethe spindle there may be a spreading. of the. fingersv 11 so as to 7cause a slipofthe spindle threads. with relation to the threads of the tap-ered. pqftionof the barrel despite theV useof the ratchet thread.`

To avoid this possibility 11i-ift 9 maybe tightened upon the exterior screw thread. at the tapered end of barrel. 6 `so as tomakeit impossible for the fingers'y 11 to spread no matter how much forc'e'is applied to rotate `the spindle. i

'.In the. modified form of my invention, shown in Fig. 3, the only change from: the details just describedcwith reference to Figs.- l and 2 consistsin thinningthe walls. ofbarrel by means of a peripheral groove. 12 in the regionof Vthe openings .10.Y By reasonof this thinning, theiiekibility o'jf the fingers. 11 is increased'.l

Fig. 5, shows an embodiment of my inventionin which the vholes 10 areomittedl-f'rom the barrel 6. This decreases the iieXibility of the 'fingers` 11, other thingsbeingequal, but this decreasedfleibility may lbecompensated for by making the slotsfdeeper. rllhe construction may, however, answer in some cases. n y

Having descfilled.,my` invention, I claim:

l.. In a micrometer Caliper, ineombination with a threaded spindle, a barrel having, an interior thread at its outer. end coperating withthe spindle. thread, said: endl being longitudinally slotted. to constitute. lingers, and

said fingers being sprung `inwardly to form ,Qitudinallyl slotted to. constitute fingers and there being holes Vbored through the barrel at.. the inner end ofxeach slot, the diameter of theholes being substantiallyequal to that ofthe width; ofthe walls ybetween the holes ywhereby the wall off thebarrel between the holes.y acts asa fiat spring.

3. In ammrometer caliper, vin. combinationglitudinally slotted to constitute fingers and t 1ere being holes bored through the barrel at the inner end of each slot whereby the wall of the barrel between the hole acts as a dat spring, said Iingers being sprung inwardly to form an opening of a smaller diarneter than that of the spindle before said spindle is threaded into the barrel.

In testimony whereof have hereunto set my hand.

HENRY S. HUBBELL.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C. 

